After completing and testing the hardware design it was time to build the project into a decent enclosure, a couple of challenges presented themselves. How was I going neatly add a USB socket to the enclosure and how am I going to interface with the instrument cluster?
I decided to use a Neutrik USB pass-through socket as I have used them before on audio equipment. They are high quality and reversible, a USB-to-Serial device was plugged directly into this adapter as the rest of the circuit communicates via the UART on the Atmel chip.
Instrument Cluster Interface
I decided to use a 9 pin D-Sub connector. This is enough, for now, but in order to add control over the warning lights not controllable via the CAN-bus I would need to add a second connector. Using an old SCART cable I made a short extension cable.
Extra Switches and LEDs
The two switches are to simulate the car ignition, the first switch controls the permanent 12V feed. Removing this power causes the cluster to recalibrate the needles when power is reapplied. The second switch is the key “Accessory” position and brings the cluster to life. The extra LEDs on the enclosure are “Heartbeat” LEDs that blink slowly, when data is received the LEDs blink faster. There’s two because a separate microcontroller on a separate board is used to handle K-Bus communication via I2C.